Hurricane category 6 could be introduced under new storm severity scale

Wind (from old system, 1min sustained speeds) Cat 1: 33–42 m/s (~74–95 mph) Cat 2: 43–49 m/s (~96–110 mph) Cat 3: 50–58 m/s (~111–129 mph) Cat 4: 59–69 m/s (~130–156 mph) Cat 5: >70 m/s (>157 mph) Storm surge (peak surge height above tide) Cat 1: 0.75–1.54 m Cat 2: 1.55–2.34 m Cat 3: 2.35–3.14 m Cat 4: 3.15–3.99 m Cat 5: >4.00 m Accumulated rainfall (event total) Cat 1: 100–262 mm Cat 2: 263–425 mm Cat 3: 426–588 mm Cat 4: 589–749 mm Cat 5: >750 mm

And the following criteria:

(a) The final category can never be lower than the highest hazard-based category;

(b) The TCSS should adequately reflect the case of high potential risk of two or more hazards. We consider a hazard of high risk when its respect- ive category is classified as 3 or higher (equal to the definition for a Major Hurricane on the SSHWS). Whenever (at least) two high risk haz- ards have the same category value and the third hazard has a lower category value, the final category should increment the highest hazard- based category. This implies that a TC scoring a Category 3 on both wind and storm surge, and a Category 1 on rainfall, will be classified as a Category 4.

(c) To warn the general public for an event with multiple extreme hazards, a high-risk TC can be classified as a Category 6 when either 1. at least two of the hazard-based categories are of Cat- egory 5; or 2. two categories are of Category 4, and one of Category 5.